Were the tank straps painted black or left galvanized? Also was the insulator between the strap and tank felt or rubber?

All the original cars I have inspected have had the straps painted black with no insulators under the strap. The felt insulators go on top of the tank.

Correct - The vendors somehow feel compelled to sell insulators that go between the straps and the tank, but the cars were never built that way; the insulators go on top of the tank, as shown in the Assembly Manual.

None of the factory built cars have insulators under the fuel tank straps. That is something that resto places had marketed to the general Camaro public. Most of the original cars that I've seen have painted black straps.